High-frequency supply



June 7, 1932. R. c CURTIS 1,861,437

HIGH FREQUENCY SUPPLY Filed March 12, 1929 Resonant Relay Conh'olDevices INVENTOR Richard C.Curt1s ATTORNEY Patented June 7, 1932 UNITEDSTATES PATENT OFFICE RICHARD G. CURTIS, OF WILKINSIBURG, PENNSYLVANIA,ASSIC-NOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, ACQRPOB-ATION OF PENNSYL- VANIA HIGH-FREQUENCY SUPPLY Application filedMarch 12, 1929. Serial No. 346,359.

This invention concerns means for supplying a high-frequency current toa distribution circuit.

Numerous control and protective systems have recently been proposedwhich make use of a high-frequency alternating current superposed uponconductors which also carry the relatively low-frequency power currentof a distribution system. Two particular applications of systems of thistype are found in protective systems for railway distribution circuitsand remote control of streetlighting systems.

One of the outstanding diflic-ulties which is common to the systems ofthese types proposed heretofore is in the means for supplying thehigh-frequency control or protective current to the circuit conductorsand it is the principal object of this invention to provide an improvedmethod of, and means for, supplying such current to a distributioncircuit of the usual type.

It is a further object of my invention to provide a system of the typedescribed in which the necessary auxiliary equipment is insulated fromthe conductor of the system to which it is applied, so that it may bereadily utilized in connection with high-voltage systems.

Another object of my invention is to provide a high-frequency supplywhich need be designed to withstand only a relatively low voltage sinceit is not to be electrically connected across the distribution circuit,in the usual manner, or to any point thereof.

A further object of my invention is to make provision for adjustment ofthe constants of the auxiliary circuit utilized to supply thehigh-frequency current, so that the impedance of the circuit traversedby the high-frequency current shall be a minimum.

Another object of the invention is to eliminate the auxiliary tuningequipment which has been used heretofore in similar systems.

5 t is well known, that in order to supply a high-frequency current to adistribution system, some form of inductive reactance in connection withcapacitive reacta-nce is required .to feed the high-frequency currentinto the system and, at the same time, to prevent the flow oflow-frequency current in the auxiliary supply circuit. It has beencustomary, heretofore, to place the condenser or reactance or both indirect connection with highvoltage power circuits.

In accordance with my invention,Iutilizea current transformer, theprimary winding of which I connect in circuit with one of the conductorsof the distribution system. The secondary winding is connected to theauxiliary supply of low-frequency control current. This transformerserves to insulate the auxiliary supply circuit from the high voltage ofthe distribution system. The reactor, which is necessary in suchcircuit, is connected across the transformer secondary and an auxiliary,high frequency generator is connected, in series with a blockingcondenser, across a portion of the secondary winding of the transformer.

For a thorough understanding of my invention, reference must be made tothe accompanying drawing, the single figure of which is a diagrammaticillustration of my invention.

Referring to the drawing, a distribution circuit is illustrated at 10and is adapted to receive energy, in the form of alternating current,from any suitable source, such as the generator 11, through a powertransformer 11. A plurality of load devices or control elements, such asa lamp 12 and a circuit breaker 13, are adapted to be controlled bymeans of a relatively high-frequency control current supplied to thecircuit 10 from an auxiliary source, such as the generator 14.Controlling equipment, indicated schematically at 15 and 16, may beemployed to control the operations of the load and switching devices 12and 13. An example of such control means which is responsive tohigh-frequency currents will be found in the U. S. patent to Lunt, No.706,575.

The primary winding of a current transformer 17 is connected in serieswith one conductor of the circuit 10. The secondary winding of thetransformer is provided with a plurality of variable taps, and avariable reactor 18 is adapted to be connected across a portion of thesecondary winding. The resecondary and the reactor with variable tapsactance of the condenser 19.

is to make possible the adjustment of the inductive reactanceattributable to the reactor 18, the generator 14:, the transformer 17and the circuit 10, equivalent to the capacitive re- WVhen thisadjustment has been effected, it will be understood that the circuittraversed by the highfrequency current will be of minimum impedance tosuch current and, that at the same time, a high impedance for thelow-frequency current will be afforded, to prevent circulation of thelatter through the auxiliary supply circuit.

The operation of the control equipment illustrated at 15 and 16 may beeffected varying the speed of the generator let to supply current of theparticular frequency necessary to accomplish the desired operation. Theauxiliary supply apparatus may be disconnected as soon as opportunityhas been given for the operation of the distant apparatus.

It will be apparent that the system of my invention makes possible amarked reduction in the cost of the equipment necessary to sup ply ahiglrfrequency current to a distribution system, since it eliminates thenecessity for designing the required apparatus to with stand the highvoltages characteristic of modern distribution systems. An additionaladvantage characteristic of my invention is that, since the directconnection between the auxiliary apparatus and the high-voltage line isobviated, a degree of safety not attained heretofore is afforded theoperators of the apparatus. I

Since alterations and modifications in the embodiment of my inventionherein shown and described will doubtless occur to those skilled in theart, it isnot my intention to be limited to such illustrated embodimentexcept as necessitated by the appended claims.

I claim as my invention:

, 1. The combination with a main power circuit, of a series transformerhaving a primary winding connected therein for introducing a controlcurrent thereto, a shunting reactor variably connected across thesecondary winding of said transformer, and an auxiliary, high-frequencygenerator and a blocking condenser variably connected in series across aportion of said secondary winding to provide a generator circuit whichmay be tuned to series resonance with the main power circuit.

2. In a high-frequency supply for controlling a distribution system, thecombination with a series insulating transformer having a primarywinding connected in series with a conductor of said system, of avariable reactor for shunting a portion of the secondary winding of saidtransformer to provide a lowimpedance circuit, and a high-frequencygenerator and a blocking condenser connected in series across a portionof said secondary winding.

3. A system for impressing a high-frequency control current upon a powercircuit carrying power at commercial frequency comprising incombination, a high-frequency generator for supplying control currentsof predetermined frequencies, a current transformer having primary andsecondary windings interposed between the generator and the powercircuit, said primary winding being connected in series with the powercircuit, a condenser, means for variably connecting the generator andcondenser in series circuit relation across the secondary winding of thecurrent transformer to provide a circuit which may be tuned to seriesresonance with the power circuit, a variable reactor, and means forconnecting the variable reactor across the secondary winding of thetransformer to provide a low-impedance circuit to function as a by-passto the generator circuit for the power current flowing in the powercircuit.

4. A system for impressing a control current of predetermined frequencyon a power circuit comprising a generator for supplying a high-frequencycontrol current, a current transformer having its primary windingconnected in the power circuit, a condenser disposed to be connected inseries with the generator across a portion of the secondary winding ofthe current transformer, a reactor, means for connecting the reactor inshunt relation to the secondary winding to provide a low-impedancecircuit to by-pass the power current and means for variably connectingthe generator and condenser across the secondary winding of the currenttransformer to provide a generator circuit which may be tuned to seriesresonance with the power circuit.

5. A system for supplying control current of predetermined highfrequency to a distribution circuit connected to a power sourcecomprising in combination, a current transformer having its primarywinding connected in the distribution circuit, a reactor connected inparallel-circuit relation to the secondary winding of the currenttransformer to provide a low-impedance circuit for power current, anauxiliary generator for supplying control current of predetermined highfrequency, a condenser connected in series with the generator, and meansfor variably connecting the generator and condenser in shunt relation tothe secondary winding of the current transformer to provide aseriesresonance circuit to cause the Voltage induced in the primarywinding of the current transformer to be increased over the normal valueproduced by the auxiliary generator.

6. A system for impressing a control current of separate frequency on apower circuit comprising in combination, a generator for supplyingcontrol current of separate fre quency, a current transformer having itsprimary winding connected in the power circuit, a reactor variablyconnected to the secondary winding of the current transformer to providea low-impedance circuit for passing power currents, a condenser, andmeans for variably connecting the generator and condenser inseries-circuit relation across the secondary winding of the currenttransformer to provide a circuit which may be tuned to series resonancewith the power circuit whereby the generator voltage is caused to beamplified through the functioning of the series-resonance circuit.

7. In combination, a transformer having primary and secondary windings,a generator and a condenser connected in series across the secondarywinding of the transformer, and a variable inductance also connectedacross the secondary winding, whereby the generator circuit may be tunedto series resonance with a power circuit in which the primary winding ofthe transformer is disposed to be connected.

8. In a system for supplying high frequency control current to a powercircuit comprising, in combination, a current transformer having itsprimary winding connected in the power circuit, an auxiliaryhighfrequency generator variably connected in series across a portion ofthe secondary winding of the transformer and a shunting reactor variablyconnected across the secondary winding, whereby the capacitive andinductive reactance of the circuits may be adjusted to a predeterminedrelation.

In testimony whereof I have hereunto subscribed my name this 9th day ofMarch, 1929.

RICHARD C. CURTIS.

